/**
 * JDBM LICENSE v1.00
 *
 * Redistribution and use of this software and associated documentation
 * ("Software"), with or without modification, are permitted provided
 * that the following conditions are met:
 *
 * 1. Redistributions of source code must retain copyright
 *    statements and notices.  Redistributions must also contain a
 *    copy of this document.
 *
 * 2. Redistributions in binary form must reproduce the
 *    above copyright notice, this list of conditions and the
 *    following disclaimer in the documentation and/or other
 *    materials provided with the distribution.
 *
 * 3. The name "JDBM" must not be used to endorse or promote
 *    products derived from this Software without prior written
 *    permission of Cees de Groot.  For written permission,
 *    please contact cg@cdegroot.com.
 *
 * 4. Products derived from this Software may not be called "JDBM"
 *    nor may "JDBM" appear in their names without prior written
 *    permission of Cees de Groot.
 *
 * 5. Due credit should be given to the JDBM Project
 *    (http://jdbm.sourceforge.net/).
 *
 * THIS SOFTWARE IS PROVIDED BY THE JDBM PROJECT AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
 * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
 * CEES DE GROOT OR ANY CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Copyright 2000 (C) Cees de Groot. All Rights Reserved.
 * Contributions are Copyright (C) 2000 by their associated contributors.
 *
 * $Id: LogicalRowIdManager.java,v 1.3 2005/06/25 23:12:32 doomdark Exp $
 */

package com.sunchangming.stmdb.recman;

import java.io.IOException;

/**
 * This class manages the linked lists of logical rowid pages.
 */
final class LogicalRowIdManager {
	// our record file and associated page manager
	private final RecordFile file;
	private final PageManager pageman;
	private final FreeLogicalRowIdPageManager freeman;

	/**
	 * Creates a log rowid manager using the indicated record file and page
	 * manager
	 */
	LogicalRowIdManager(RecordFile file, PageManager pageman) throws IOException {
		this.file = file;
		this.pageman = pageman;
		this.freeman = new FreeLogicalRowIdPageManager(file, pageman);

	}

	/**
	 * Creates a new logical rowid pointing to the indicated physical id
	 */
	Location insert(Location loc) throws IOException {
		// check whether there's a free rowid to reuse
		Location retval = freeman.get();
		if (retval == null) {
			// no. This means that we bootstrap things by allocating
			// a new translation page and freeing all the rowids on it.
			final long firstPage = pageman.allocate(Magic.TRANSLATION_PAGE);
			short curOffset = TranslationPage.O_TRANS;
			for (int i = 0; i < TranslationPage.ELEMS_PER_PAGE; i++) {
				freeman.put(new Location(firstPage, curOffset));
				curOffset += PhysicalRowId.SIZE;
			}
			retval = freeman.get();
			if (retval == null) {
				throw new Error("couldn't obtain free translation");
			}
		}
		// write the translation.
		update(retval, loc);
		return retval;
	}

	/**
	 * Releases the indicated logical rowid.
	 */
	void delete(Location rowid) throws IOException {

		freeman.put(rowid);
	}

	/**
	 * Updates the mapping
	 * 
	 * @param rowid
	 *            The logical rowid
	 * @param loc
	 *            The physical rowid
	 */
	void update(Location rowid, Location loc) throws IOException {

		final TranslationPage xlatPage = TranslationPage.getTranslationPageView(file.get(rowid.getBlock()));
		final PhysicalRowId physid = xlatPage.get(rowid.getOffset());
		physid.setBlock(loc.getBlock());
		physid.setOffset(loc.getOffset());
		file.release(rowid.getBlock(), true);
	}

	/**
	 * Returns a mapping
	 * 
	 * @param rowid
	 *            The logical rowid
	 * @return The physical rowid
	 */
	Location fetch(Location rowid) throws IOException {

		final TranslationPage xlatPage = TranslationPage.getTranslationPageView(file.get(rowid.getBlock()));
		try {
			final Location retval = new Location(xlatPage.get(rowid.getOffset()));
			return retval;
		} finally {
			file.release(rowid.getBlock(), false);
		}
	}

}
